An active matrix substrate that is used in a liquid crystal display device or the like has a display area that has multiple pixels and an area (a non-display area or a frame area) other than the display area. Included in the display area is a switching element such as a thin film transistor (hereinafter referred to as “TFT”) for every pixel. As such a switching element, a TFT of which an activation layer is an amorphous silicon film (hereinafter referred to as “amorphous silicon TFT”), or a TFT of which an activation layer is a polycrystalline silicon film (hereinafter referred to as “polycrystalline silicon TFT”) has been widely used in the related art.
It has been proposed that instead of amorphous silicon or polycrystalline silicon, an oxide semiconductor is used as a material of the activation layer of the TFT. Such a TFT is referred to as an “oxide semiconductor TFT”. The oxide semiconductor has mobility higher than the amorphous silicon. For this reason, it is possible that the oxide semiconductor TFT operates at a speed higher than the amorphous silicon TFT.
A semiconductor chip that constitutes a drive circuit, such as a source driver or a gate driver, is mounted in a non-display area (a chip on glass (COG) mounting). In the present specification, an area, in which the semiconductor chip is mounted, of the active matrix substrate is referred to as a “semiconductor chip mounting area”. Multiple terminal portions each for connecting a terminal of the semiconductor chip and a gate bus line or a source bus line in the display area are further arranged in the non-display area. These terminal portions are formed, for example, in the semiconductor chip mounting area (that is, are arranged between the semiconductor chip and the substrate).
In some cases, a drive circuit, such as a gate driver or a source driver, is monolithically (integrally) provided in the non-display area. The drive circuit that is monolithically formed is referred to as a “monolithic driver”. The monolithic driver is normally configured using the TFT. In recent years, technologies that manufacture the monolithic driver using the oxide semiconductor TFT have been used. Accordingly, cost reduction is realized by narrowing down the frame area or simplifying a mounting process.
In recent years, in most cases, a gate driver circuit has been monolithically formed and a source driver circuit has been mounted using a COG method, in the non-display area in a device such as a smartphone and a tablet with a small size of less than 10 inches, the frame of which is strongly desired to be narrower.
In the non-display area, an inspection circuit is further provided for performing pseudo dynamic lighting inspection that is a method of detecting a failure in a liquid crystal display device (a liquid crystal display panel). Accordingly, it is possible that the failure is detected such as a disconnection or a short circuit on the active matrix substrate.
The inspection circuit includes, for example, multiple TFTs (hereinafter referred to as “inspection TFTs”). Each inspection TFT is connected to the source bus line or the gate bus line. At the lighting inspection, the inspection TFT is caused to enter an ON state, and thus an inspection signal is supplied to the source bus line or the gate bus line. After the lighting inspection, when the liquid crystal display panel normally operates, the inspection TFT is maintained in an OFF state.
In the related art, the inspection TFT is positioned between the semiconductor chip mounting area and the display area, in the non-display area on the side opposite to the side of the semiconductor chip mounting area with the display area interposed therebetween, or the like. In recent years, for the purpose of further narrowing the non-display area, a configuration has been proposed in which the inspection circuit that includes the inspection TFT is positioned within the semiconductor chip mounting area (for example, PTL 1 and PTL 2).